Then you have to point your nginx config to those folders as home folders, i.e. /var/www/ghost-news for the ghost news site.
Not sure why you chose to complicate the home folder adding system/nginx-root to it (unless you have some other important folders in that path that you do not want to be accessible from the internet). But if that is the case, Ghost should have been installed in /var/www/ghost-news/system/nginx-root/ instead of /var/www/ghost-news/.
Uhm, strange. I have to agree I have not installed a Ghost with all its default options as I have always chosen to setup my own nginx config files so I am not sure how the standard Ghost install procedure creates the nginx conf file. And my configs look like this:
I think that was because of port misconfigurations and i just uninstalled ghost from that folder and deleted that folder and made a new one and ran the ghost install command and it worked fine.